Return of the Sea Otter Read online

  But they are so much more than just the sum of their superlatives, too. One of thirteen otter species around the world, sea otters are believed to have evolved from primitive, fish-eating otter ancestors in Eurasia about five to seven million years ago. Those ancestors were probably terrestrial mammals that moved into the marine environment relatively recently—whale, dolphin, and seal ancestors took to the sea between fifteen and forty million years earlier—perhaps to escape from predators or to gain access to more abundant prey resources, like the invertebrates they likely discovered while foraging at low tide. That’s probably when they began to evolve the specific adaptations that allow them to spend most of their lives in the ocean, including rear flippers to aid in underwater locomotion, the ability to survive without consuming freshwater, an expanded lung capacity enabling them to dive beneath the surface for food, and strategies for giving birth and raising their young entirely at sea.

  Fossil evidence suggests that the sea otter genus became confined to the North Pacific one to three million years ago, with records from the early Pleistocene collected from Cape Blanco, Oregon, and Moonstone Beach, California. The only surviving member of the genus, today’s modern sea otter, is believed to have evolved along the coast of eastern Russia and northern Japan before spreading across the arc of Alaska’s Aleutian Islands and down the coast of North America.

  Living primarily in kelp-forest habitat in nearshore waters—though they sometimes use soft-sediment areas and other habitats as well—sea otters are seldom found more than a mile from shore. Estimates of their pre–fur trade numbers range from 150,000 to 300,000, but just a few remnant populations totaling fewer than 1,000 animals survived into the twentieth century. Naturally recovering populations and reintroductions into former habitat resulted in a 2015 world population of about 125,000 sea otters living in scattered locations including the coasts of central California, Washington, British Columbia, Southeast Alaska, Prince William Sound, the Aleutian Islands, and Russia’s Commander Islands.

  They aren’t all exactly alike, though. Three subspecies are recognized: the southern sea otter, found exclusively in central California; the northern sea otter, ranging from Washington to Alaska; and the common or Asian sea otter, found on the Commander Islands, the Kuril Islands of the western Pacific, and occasionally the northernmost islands of Japan. Although the Asian subspecies has long been considered the largest otter and the southern subspecies the smallest, there are actually few physical differences among them. In fact, their physical size has more to do with the availability of food than genetic differences. Sea otters living in areas where food is abundant in California are likely to be larger than otters found in areas of Alaska where food is limited, for instance, even though California otters are, on average, slightly smaller than Alaska otters.

  When food is available, sea otters are voracious eaters. They have to be. Because they have no blubber to keep them warm in the chilly waters of the North Pacific, they must consume 25 to 30 percent of their body weight in food every day. Were I in the same boat, I would have to eat nearly forty pounds of food each day just to maintain my weight. To accomplish this feat, sea otters feed on a wide range of benthic marine invertebrates, including sea urchins, clams and other mollusks, crabs of many varieties, sea cucumbers, abalone and other snails, and occasionally even fish and seabirds. As a result of their prodigious appetite, they often control prey populations and can make commercial harvest of some species unviable. That renders them especially unpopular among some fishermen, who find it impossible to compete with the highly adapted and unrestricted sea otter for several economically valuable species. But far from being entirely negative, the ability of sea otters to keep some marine invertebrates—especially sea urchins—from growing too abundant has provided benefits to entire ecosystems and made them the quintessential representative of what scientists call keystone species.

  Sea otters are apex predators in their kelp-forest habitat. They are at the top of the food chain and exert an extraordinary influence on the composition of other species found there. That influence is something discovered in the 1970s by Jim Estes, the dean of sea otter researchers in North America for the last half century. He says that keystone species are those that are “relatively rare but very important ecologically.” He compared two islands in the Aleutian chain in Alaska—Amchitka, where sea otters were abundant, and Shemya, where sea otters were hunted to extinction more than a century before—and he found dramatic differences that he concluded were the result of the sea otters’ influence. For the next several decades, he watched those and other North Pacific sites with and without otters and made an extensive variety of comparisons. Everywhere he went he found the same thing: where sea otters were plentiful, the kelp-forest ecosystem was healthy and home to numerous other species; where otters were absent, the ecosystem became what he called an “urchin barren” with hardly any kelp left at all and few other thriving species. He discovered that barnacles and mussels grew three or four times faster in kelp forests than in urchin barrens, and some species of fish could be ten times more abundant where otters and kelp were present. And it was not just the underwater world that was affected. Glaucous-winged gulls flying at the surface changed their diet in the absence of otters and kelp, switching from about 90 percent fish to 90 percent invertebrates. Bald eagles made a similar adjustment in their diet from fish, marine mammals, and seabirds when otters were present to mostly seabirds when they were not. Estes even found that sea otters influenced the carbon cycle, the movement of carbon as it is used and recycled in biogeochemical processes from the atmosphere to the oceans and back.

  “We’ve come to the view that the whole base of the structure and function of the ecosystem is influenced by the impact of otters through this trophic cascade,” Estes told me. “That, in retrospect, is a fairly predictable and not surprising finding, because when you take the plants out of the system, which is essentially what happens when you lose otters”—urchins eat all the kelp—“you’re going to influence almost everything about that system. Just like if you were to go in and clear-cut a forest, you would be hard pressed to find a species that wasn’t influenced by that. That’s pretty much the kind of process we’re talking about here.”

  Beyond their role as a keystone species in the kelp forests of the coastal North Pacific, sea otters exhibit a number of other unique characteristics that make them much more similar to unrelated marine mammals than to their closer terrestrial cousins. Rather than having flesh-tearing teeth more typical of other carnivores, they have adaptations to their teeth and jaws enabling them to bite with tremendous force and crush their hard-shelled prey. They are capable of diving more than three hundred feet beneath the sea surface, thanks to the increased oxygen-storage capacity of their large lungs and an anaerobic metabolism, similar to that in whales and seals, when especially long or deep dives are necessary. And their loosely articulated skeleton and absent clavicle enable them to be unusually flexible, providing them access via their paws and mouth to every inch of skin for whole-body grooming and for whatever movements may be necessary in their aquatic environment. Their reproductive traits have also evolved to be more similar to that of marine mammals than their relatives on land, including giving birth to a single young (rarely to twins), gestating for a relatively long period of six months, and caring for young for an extended time. Living up to twenty-five years in captivity but more often ten to fifteen years in the wild, socially they are more like marine mammals as well, gathering in sometimes large groups—usually sexually segregated—to rest and, less often, to feed.

  Perhaps, however, sea otters are most celebrated for their tool use, a skill that places them, among mammals, in the company of only humans, chimpanzees, and dolphins. Who wouldn’t be charmed by a furry creature that carries a tool—a rock, most often, but driftwood, glass bottles, and other objects as well—in a purselike pouch in its armpit while it forages for hard-shelled prey, then uses the tool to crack open
that prey while reclining on its back in the water? And when an appropriate-size tool isn’t available, they’re known to get creative by smacking shellfish against marina docks, jetties, boat hulls, and any other hard surface they can access. One study of abalone shell breakage patterns in California in the late 1960s found 80 percent of the shells had been broken by a tool likely used by a sea otter. Yet tools are used by the otters not only once they have brought their prey to the surface, but to dislodge prey from underwater rocks or crevices. Otters have also been known to begin the process of cracking open shelled prey while still submerged.

  Like jazz musicians, sea otters must constantly improvise how they use particular tools, developing new and inventive ways to gain access to their prey. The most common method is to use their belly like a picnic table, placing a rock there and smashing the prey down on the tool. They sometimes also reverse the process and use the rock as a hammer against the prey. And they have even been observed using one rock like an anvil on their belly, placing the prey item upon it, and then using a second rock to crack open the shell. When part of a shell is finally broken off, that piece often becomes a tool to further pound on the already-broken prey. And sometimes sea otters may slam one shelled animal against another until both of them reveal their flesh. As scientists spend more and more time observing sea otter foraging behavior, they are discovering an even wider variety of strategies for tool use. I’m especially intrigued by the otters that use different strategies for different prey, like one animal that used a rock for cracking turban snails and a glass bottle for prying mollusks off an underwater ledge.

  Beyond the impressive tool use, though, beyond the cuteness factor, beyond even the sea otter’s dramatic influence on its habitat, if you’re still not enamored of the sea otter, then perhaps its incredible fur coat will make you a fan. The animal’s thick pelt has led to massive human changes: sea otter fur was indirectly responsible for the establishment of a global mercantile industry, the alteration of Native American cultures, the accusation that Russians enslaved Native hunters, the first use of firearms by Natives on the British Columbia coast, the first Russian settlements on the Aleutian Islands, the deaths of hundreds (perhaps thousands) of seamen from a half dozen countries, and the establishment of new trade routes, not to mention the animal’s near extinction. All because of its fur.

  But what amazing fur it is. Thanks to their pelt, sea otters don’t need blubber to keep them warm in the icy North Pacific (though their rapid metabolism helps them stay warm, too). A freshly groomed otter has the same insulating capacity as a harbor seal with a thick layer of blubber. In fact, according to Heather Liwanag, a biology professor at Adelphi University who has compared the insulating qualities of fur and blubber, sea otters would need a layer of blubber larger than themselves to equal the insulating abilities of their pelt. Maintaining that pelt is quite a job, though. Sea otters must spend hours each day grooming themselves and blowing air into their fur to increase its thermoregulation properties, because it’s the layer of trapped air in their fur that provides the insulating power. It also makes them extremely buoyant, however, so to dive deep the animals must release some of the trapped air in a stream of bubbles as they submerge.

  Amazingly, despite living their entire lives in the water, sea otters almost never get their skin wet. Each sea otter hair is covered in tiny geometric barbs that help to mat the hairs together so tightly that water cannot penetrate to the skin. A dry otter—even when it’s in the water—is a warm otter. But that pelt of matted fur is a lot to carry around with them. When removed from its body, that fur coat—consisting of an inner insulating layer of very short, soft underfur protected by long outer guard hairs—represents about one quarter of the animal’s weight. It’s like a human wearing a forty-pound coat around just to keep the chill off, and then being unable to remove it when the temperature rises. Lucky for the otters, their watery habitat never gets too warm.

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  UNFORTUNATELY, that luxurious fur has historically been the sea otter’s greatest vulnerability, and in some places it remains so today. Demand for sea otter furs among merchants in Canton, China, in the late 1700s and early 1800s drove the animals to near extinction as a result of an active ship-based trading system that developed throughout the North Pacific. For more than half a century, Russian, British, and American merchant ships competed for access to sea otter pelts harvested mostly by Native peoples from California to the outer reaches of Alaska and beyond.

  Demand for furs of all varieties was high in China, and prior to the European exploration of the North Pacific and the northwest coast of North America, that demand was primarily met by Russian traders, who delivered as many as a million furs each year—primarily otter, lynx, squirrel, fox, and sable—from Siberia to China. In the 1760s, Russia began a commercial expansion eastward across the Aleutian Islands, and by the end of the decade, all of the Aleutians had been explored for their potential to yield valuable furs that could be sold in China. Sea otter pelts were found to be the most valuable fur by far. A handful of well-financed Russian merchants established permanent settlements on some islands, hired local Natives to capture sea otters, and eventually banded together to establish the Russian-American Company to control the Alaska fur trade.

  By then, though, British and American merchants heard about the money that could be made from sea otter pelts in China and rushed to Alaska and British Columbia to enter what would become known as the North West Coast trade. British captain James Cook’s third voyage of discovery explored the coast of Alaska and the Bering Strait, and along the way acquired sea otter pelts for one shilling apiece that, in 1779, they traded in China for $120 (or a profit of 1,800 percent). When unauthorized reports of Cook’s voyage were published in Britain and New England several years later, the rush was on to trade European and American trinkets, raw materials, guns, and textiles with the North West Coast Natives for sea otter pelts, which were then traded to Chinese merchants for tea, silks, porcelain, and other products that were in great demand back in European and American ports.

  Sea otter pelts were quickly considered the most desirable and most valuable furs in the world, used primarily to line winter clothing. The best were glossy black and could be more than five feet long and three feet wide. The Chinese graded sea otter pelts in up to ten classes, while the Russians subdivided them into four categories based on the size of the pelt and the length and softness of the fur. Pelts from Russia’s Kuril Islands and Kamchatka Peninsula were considered the best—which led to the otters in that region becoming extirpated first—followed by otter furs from the Aleutian Islands, the North West Coast, and California.

  Native groups along coastal Alaska and British Columbia, including Chinook, Nootka, Salish, Haida, and Tlingit people, prized sea otter pelts for their warmth and beauty long before the coastal trade began. Some tribes allowed only their chiefs and other leaders to wear clothing made from sea otter fur. But the animals weren’t easy to hunt—it was considered more dangerous than whaling—because sea otters are smart, cagey, excellent swimmers, and aggressively defensive of their young. Yet because they were already skilled otter hunters, it was relatively easy for the Natives to intensify their hunting effort to meet the demands of the trading vessels.

  Initially, the Native peoples traded furs to acquire iron for making fishhooks, arrowheads, knife blades, and lance tips, and copper for fashioning into bracelets and other adornments. Later they sought cotton cloth, firearms, molasses, and rum. In 1796, one otter skin brought two yards of blue cloth at Clayoquot Sound and six yards at Nootka Sound, both on the west coast of Vancouver Island. But by 1826, when sea otters had become scarce, the price was twelve yards of cloth. One ship visiting the Queen Charlotte Islands (now Haida Gwaii) in 1812 was reported to have traded four blankets, four buckets of molasses and rice, an axe, and other gifts for one sea otter skin.

  In the early going, it was the Russians who led the trade by employing what many
considered the best sea otter hunters, Native Aleuts and Kodiak Islanders. Unlike the Americans and British, who only traded and transported furs, the Russians commanded hundreds of Alaska Natives to hunt for them in kayaks. The hunters would typically be directed to start in March or April, with upwards of 150 kayaks setting out from Kodiak Island, 100 from Unalaska Island, and 50 from Atka Island (and sometimes smaller numbers from Cook Inlet and Prince William Sound), and proceed to designated locations along the coast, where they stayed through the summer. At the end of the season, they submitted the animals they harvested for three to thirty rubles per skin, depending on the grade of the pelt.

  When the British entered the trade following Cook’s voyage, the rush for otter skins was on. In 1785, Captain James Hanna and a crew of thirty were the first to arrive, having traveled around South America to Nootka Sound on a sixty-ton brig renamed the Sea Otter. They acquired 560 otter skins in five weeks and sold them in China a year later for $24,000. By then six other British ships were trading along the North West Coast, including several that were led by former members of Cook’s expedition, one of whom claimed that “the fur trade is inexhaustible wherever there are inhabitants.” But British involvement in the fur trade all but ended by the turn of the nineteenth century, primarily due to conflicts with the East India Company and the South Sea Company, which had monopolies on British trade in the Pacific and in China. By the time the trade monopolies were abolished in 1834, there were few otters left to buy and fur was falling out of fashion.

  For much of the period, the trade was dominated by American ships, most of which originated in Boston. Throughout the 1790s, American vessels annually traded goods valued, on average, at about $62,000 to acquire from Native groups furs that brought in $350,000 in China. A decade later, the value of the furs in China was three or four times greater. But by the 1810s, the trade slowed because too many ships were chasing too few otters. And while the fur trade continued for several more decades, the financial return declined dramatically as sea otters became more and more scarce. By 1841, the last of the American vessels withdrew and the trade was all but over.